Display telephone sets are well-known in the art. When they are used with a switching system that is designed for use with display telephone sets, they typically display to a caller the telephone number that he or she is dialing. As the caller inputs the digits of the number on the telephone set, the digits are sent to the switching system, which echoes (returns) them to the display of the caller's telephone set.
In many such systems, the displayed dialed number is visually segmented--divided into its components--by dashes. These are not dialed or otherwise input by the caller, but are generated by the call-processing function of the switching system.
The switching system is typically capable of properly segmenting the dialed number into its logical components only if the dialed number is a number of the local network numbering plan of the switching system or has the same pattern (i.e., the same number of logical components each having the same number of digits) as the numbers of the local network numbering plan. But this capability breaks down for other dialable numbers.
Thus, for example, a switching system designed for use with the North American numbering plan as the local numbering plan would display the dialed number "0117758900" (or any other 10-digit number) as "011-775-8900", reflecting standard components of the North American numbering plan: area code-office (exchange) code-extension. But in reality, the dialed number is an international numbering plan number and not a North American numbering plan number, and its intended meaning is: international code-country code-city code-location code. Hence, the number should properly be displayed as "011-77-58-900". Conventional switching systems are not able to make this distinction due to their design, which is based on assumptions about the format of the network numbering plan, and which hard-codes these assumptions into the call-processing software. A further limitation on the ability of conventional switching systems to differentiate between numbers of different network numbering plans and to properly segment them is their call-processing strategy of recognizing only the first few significant digits of a dialed number, and then taking action on the basis of those few digits while depending upon some other, down-stream, one or more network elements to recognize and handle the rest of the dialed number.
A related display capability that exists in some systems is one which replaces or supplements certain displayed dialed numbers each with the name of the person or facility to which the dialed number corresponds. This capability is provided either directly by a caller's own intelligent terminal or by the originating switching system. Because it depends for its implementation upon a pattern-matching type of translation of the dialed number into the corresponding information, this capability suffers from the disadvantages of being able to display the corresponding information only after the entire dialed number has been input by the caller, and of being limited by database-size considerations to providing this corresponding information to only a small subset of all numbers that the caller can validly input.
A further related capability, available in advanced telecommunications systems such as ISDN systems, either replaces or supplements the displayed dialed number with an identifier (e.g., a name) or a number of the endpoint to which the dialed call is being routed, or to which it has been routed and connected. Like the previously-mentioned capability, it also is able to display this endpoint-related information only after the entire dialed number has been input by the caller, and furthermore only after the route for the call has been selected and established. This is because either a database that stores endpoints-related information is relied on to provide this information, or the endpoint itself is relied on to provide this information upon being accessed. In either case, however, because the information is particularly identified with the endpoint and hence is properly understood within the context of that endpoint, it may take the form of a properly-segmented dialable sequence in all instances.